1. Field of the Invention
The present invention relates to a so-called two phase stepper motor in which each pair of conductors which is wound around each of two bobbins in different phase is disposed outside of a rotating shaft so that by sequentially applying input pulses through each conductor, the motor rotates through a predetermined angle.
The stepper motors of the type described have suddenly become very important since the development and uses of ICs advanced widely so that processing of digital signals can be carried out in a simple and economical manner.
2. Description of the Prior Art
First referring to FIGS. 1, 2, 3 and 4 of the accompanying drawings, the conventional stepper motors of the type described above will be explained prior to the detailed description of the present invention for the sake of better understanding thereof.
A conventional stepper motor as shown in FIGS. 1 and 2, has a pair of stator units 2 and 3 which have different phases disposed in parallel in the vicinity of a rotating shaft 1 and bobbins 6 and 7 around which are wound conductors 4 and 5, housed in the stator units 2 and 3. A pair of terminal processing units in the form of a metal pin are extended from both ends of the bobbin 6 in the radial direction. In like manner, a pair of terminal processing units are extended radially from both ends of the bobbin 7. The end portions 4A and 4B; 5A and 5B of the conductors 4 and 5 are wound around the processing units 4A and 4B; 5A and 5B so that they are electrically interconnected. Furthermore, the bobbins 6 and 7 are so housed within the stator units 2 and 3 that the terminal processing units 8A and 8B; 9A and 9B are in opposing relationship with each other. The terminal processing units 8A and 8B; 9A and 9B are extended outwardly through an opening 10 defined at the adjacent portions of the stator units 2 and 3. It follows therefore that the terminal processing units 8A and 8B; 9A and 9B are arranged in two rows in the axial direction.
Next referring to FIGS. 3 and 4, a second conventional stepper motor will be described. Like the first conventional stepper motor of the type described above with reference to FIGS. 1 and 2, the bobbins 6 and 7 are so disposed that the processing terminal units 8A and 8B; 9A and 9B extended from the bobbins 6 and 7 are arranged at one end portion of the rotating shaft 1 in the axial direction thereof. Therefore the terminal processing units 8A and 8B; 9A and 9B are arrayed in two rows and spaced apart from each other by a suitable direction in the axial direction. The bobbins 6 and 7 are housed within a stator unit 12 and the terminal processing units 8A and 8B; 9A and 9B are extended outwardly through an opening 13 defined in the stator unit 12. The remaining component parts are arranged in a manner substantially to that of the first conventional stepper motor described above with reference to FIGS. 1 and 2.
However, since in the first and second conventional stepper motors of the types described above, the terminal processing units 8A and 8B; 9A and 9B are arrayed in two rows in the axial direction, the portions of the stator units 2, 3 and 12 through which are extended the terminal processing units 8A and 8B; 9A and 9B outwardly must be defined widely through the outer walls of the stator units 2, 3 and 12. Especially in case of the small-sized stepper motors, it becomes difficult to secure a wide portion through which the terminal processing units 8A and 8B; 9A and 9B are extended outwardly.